First of all, let me thank the webmaster for this puzzle. It is, without question, the most difficult of any puzzle ever posted on this site.
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Needless to say, I had a tough time with this one -- until I realized that the square at the bottom left hand corner could not be a seven. Until that realization, I spent an embarrassing amount of time staring blankly at the puzzle, making no progress at all.

Very hard indeed. Part of my problem in understanding the discussion thread for this puzzle is that I'm unfamiliar with the numbering scheme. R and C for row and column are clear but are columns left to right or right to left, and rows top to bottom or bottom to top? Ditto "boxes": I'm accustomed to calling a cell a square and a 9-cell squiggly (or a straight 3x3 in a standard sudoku) a box. It may be that I'm on the wrong side of the Atlantic, but I could use clarification of everybody's notation.

Weren't there some posts from Steve on this puzzle? I can't seem to find them now that I've registered. RogerC's responses seemed on point, but I can't find them either. Is there something I don't know about how the forum works?

One other issue: I read in an academic paper on the subject (Cornell U. Math Department) that 23 "givens" are required to determine a single solution. It didn't discuss squigglies and, frankly, I didn't understand the rather off-hand proof, so it may not apply for squigglies. This puzzle is very short on givens. Anyone have any relevant info or comment?

This whole post sounds pretty feeble, but I really thought I'd gotten pretty good at this stuff (have happily solved all Standard "Very Hard" and all Squiggly "Hard" (and a couple of "Very Hard") that I've tried thus far (granted it's only been for the last couple of months).